1. Field of the Invention
This invention relates to intravascular expandable devices and delivery systems for implantation within a vessel of the body, and more particularly to an expandable stent and delivery system which may be used in the treatment of blood vessel disorders. More specifically, the expandable stent and delivery system may be used in the treatment of blood vessel blockage and aneurysms which occur in the brain.
2. Description of the Prior Art
On a worldwide basis, nearly one million balloon angioplasties were performed in 1997 to treat vascular disease, including blood vessels clogged or narrowed by a lesion or stenosis. The objective of this procedure is to increase the inner diameter or cross-sectional area of the vessel passage, or lumen, through which blood flows.
In an effort to prevent restenosis without requiring surgery, short flexible cylinders or scaffolds, made of metal or polymers, are often placed into a vessel to maintain or improve blood flow. Referred to as stents, various types of these devices are widely used for reinforcing diseased blood vessels, for opening occluded blood vessels, and for defining an internal lumen to relieve pressure in an aneurysm. Stents allow blood to flow through the vessels at an improved rate while providing the desired lumen opening or structural integrity lost by the damaged vessels. Some stents are expanded to their proper size by inflating a balloon catheter, referred to as xe2x80x9cballoon expandablexe2x80x9d stents, while others are designed to elastically resist compression in a xe2x80x9cself-expandingxe2x80x9d manner.
Balloon expandable stents and self-expanding stents are generally delivered in a cylindrical form, compressed to a smaller diameter and are placed within a vessel using a catheter-based delivery system. When positioned at a desired site within a vessel, these devices are expanded by a balloon, or allowed to xe2x80x9cself-expand,xe2x80x9d to the desired diameter.
U.S. Pat. No. 4,768,507 entitled, xe2x80x9cIntravascular Stent and Percutaneous Insertion Catheter System for the Dilation of an Arterial Stenosis and the Prevention of Arterial Restenosisxe2x80x9d discloses a system used for placing a coil spring stent into a vessel for the purposes of enhancing luminal dilation, preventing arterial restenosis and preventing vessel blockage resulting from intimal dissection following balloon and other methods of angioplasty. The coil spring stent is placed into spiral grooves on an insertion catheter. A back groove of the insertion catheter contains the most proximal coil of the coil spring stent which is prevented from springing radially outward by a flange. The coil spring stent is deployed when an outer cylinder is moved proximally allowing the stent to expand.
Also, U.S. Pat. No. 6,126,684 entitled, xe2x80x9cApparatus and Methods for Placement and Repositioning of Intraluminal Prosthesesxe2x80x9d discloses a delivery catheter for a radially compressible tubular prosthesis including an elongated shaft slideably received within an elongated sheath. The prosthesis is carried over the distal end of the shaft where it is contained in a radially compressed configuration by the sheath. Penetrating stay members on the exterior of the shaft engage the proximal section of the prosthesis allowing the prosthesis to be recaptured prior to full release of the prosthesis.
Another stent and delivery system is disclosed in U.S. Pat. No. 6,214,036 entitled, xe2x80x9cStent Which is Easily Recaptured and Repositioned Within the Body.xe2x80x9d This patent discloses a self-expanding stent which may be used in the treatment of aortic aneurysms. This device includes longitudinal legs having a flange which attaches to a delivery apparatus. The stent may be easily recaptured after placement and repositioned to a new position within the vessel. This patent, assigned to a related company, is subsequently referred to and the disclosure therein is incorporated and made a part of the subject patent application.
U.S. Pat. No. 6,361,558 entitled, xe2x80x9cStent Aneurysm Treatment System and Methodxe2x80x9d and assigned to the same assignee as the present application discloses other stent devices. This patent discloses vasculature stents of various configurations which may be used as aneurysm covers for occluding, or partially occluding, aneurysms located at various positions along the blood vessels.
In accordance with one aspect of the present invention, there is provided an expandable stent and delivery system. The delivery system includes an elongated core member having a proximal cylindrical member disposed about the core member. An intermediate cylindrical member is disposed about the core member generally positioned distally from the proximal cylindrical member and spaced apart from the proximal cylindrical member to form a first gap. A distal cylindrical member is disposed about the core member generally positioned distally from the intermediate cylindrical member and spaced apart from the intermediate cylindrical member to form a second gap.
The expandable stent includes at least one proximal leg which extends proximally from the proximal end of the stent. The stent also includes at least one distal leg which extends distally from the distal end of the stent. The stent further includes at least one anchor member attached to the proximal leg and at least one anchor member attached to the distal leg. The anchor members have a longitudinal length less than the longitudinal length of the first and second gaps and are inwardly projected in a direction toward the longitudinal axis of the stent. The stent is mounted on the intermediate cylindrical member and positioned such that the anchor members interlock within the gaps.
The delivery system further includes a deployment catheter disposed about the core member such that the deployment catheter constrains the expandable stent about the intermediate cylindrical member causing the anchor members to be maintained in the gaps and thereby causing the stent to be interlocked onto the core member.
In accordance with another aspect of the present invention, there is provided an expandable stent and delivery system. The delivery system includes an elongated core member with a proximal cylindrical member disposed about the core member. A distal cylindrical member is disposed about the core member generally positioned distally from the proximal cylindrical member and spaced apart from the proximal cylindrical member to form a gap. The expandable stent includes an anchor member attached to the stent. The anchor member has a longitudinal length less than or approximately equal to the longitudinal length of the gap and is inwardly projected in a direction toward the longitudinal axis of the stent. The stent is mounted on at least one cylindrical member and positioned such that the anchor member interlocks within the gap.
The delivery system further includes a deployment catheter disposed about the core member such that the deployment catheter constrains the expandable stent about at least one cylindrical member causing the anchor member to be maintained in the gap and thereby causing the stent to be interlocked onto the core member.
In accordance with a further aspect of the present invention, there is provided an expandable stent and delivery system. The delivery system includes an elongated core member with a plurality of cylindrical members disposed about the core member and spaced apart to form a plurality of gaps. The expandable stent includes a plurality of anchor members attached to the stent. The anchor members have a longitudinal length less than the longitudinal length of the gaps and are inwardly projected in a direction toward the longitudinal axis of the stent. The stent is mounted on at least one cylindrical member and positioned such that the anchor members interlock within the gaps.
The delivery system further includes a deployment catheter disposed about the core member such that the deployment catheter constrains the expandable stent about at least one cylindrical member causing the anchor members to be maintained in the gaps and thereby causing the stent to be interlocked onto the core member.
In accordance with a further aspect of the present invention, the elongated core member is tapered such that the proximal section of the core member has a diameter which allows the core member to be pushed through a blood vessel and the distal section of the core member has a diameter less than the diameter of the proximal section of the core member.
In accordance with still another aspect of the present invention, the expandable stent includes two proximal legs extending proximally from the proximal end of the stent and two distal legs extending distally from the distal end of the stent. Two anchor members are attached to the proximal legs, and two anchor members are attached to the distal legs. The anchor members have longitudinal lengths less than the longitudinal lengths of the gaps and are inwardly projected in a direction toward the longitudinal axis of the stent.
In accordance with another aspect of the present invention, the proximal, intermediate, and distal cylindrical members take the form of flexible coils.
In accordance with a further aspect of the present invention, a method is provided for deploying an expandable stent within a blood vessel to enhance luminal dilation of the blood vessel or to treat an aneurysm. The method includes the step of providing an expandable stent and delivery system. The expandable stent is mounted on at least one cylindrical member along a core member of the delivery system. The stent has at least one anchor member which is interlocked within at least one gap along the core member. The gaps are formed by spaces between a plurality of cylindrical members disposed on the core member. The delivery system includes a deployment catheter disposed about the stent which maintains the stent in a constrained configuration.
The method further includes the step of inserting the expandable stent and delivery system into a blood vessel and positioning the expandable stent adjacent to a blockage area or aneurysm within the vessel. The method also includes moving the deployment catheter proximally allowing the stent to begin expanding within the vessel, then again moving the deployment catheter proximally allowing the stent to fully deploy causing the vessel to increase in luminal dilation or causing the stent to cover the aneurysm. Finally, the method includes removing the delivery system from the blood vessel.
In accordance with still another aspect of the present invention, a method is provided for resheathing an expandable stent onto a delivery system within a blood vessel. The method includes the step of providing an expandable stent and delivery system. The expandable stent is mounted on at least one cylindrical member along a core member of the delivery system. The stent has at least one anchor member interlocked within at least one gap along the core member. The gap is formed by spaces between a plurality of cylindrical members disposed on the core member. The delivery system includes a deployment catheter disposed about the stent which maintains the stent in a constrained configuration. The method further includes inserting the expandable stent and delivery system into the vessel. The method also includes moving the deployment catheter proximally allowing the stent to begin expanding within the vessel. In addition, the method includes moving the deployment catheter distally which forces the stent back onto the cylindrical member of the delivery system. Finally, the method includes removing the stent and delivery system from the blood vessel or repositioning the stent and delivery system within the blood vessel.
These and other aspects of the present invention and the advantages thereof will be more clearly understood from the foregoing description in drawings of a preferred embodiment of the present invention.